"make distcheck" broken on master

[bwbarrett]

Tonight's nightly tarball build failed on master, due to a problem with libevent:

Starting build for master
Found new revision 09ad725
Exceuting run-with-autotools.sh failed:
    am__remove_distdir=: am__skip_length_check=: am__skip_mode_fix=: distdir)
make[3]: Entering directory '/mnt/data/nightly-tarball/scratch/openmpi/master-201808100242/ompi.git/opal/mca/dl/libltdl'
make[3]: Leaving directory '/mnt/data/nightly-tarball/scratch/openmpi/master-201808100242/ompi.git/opal/mca/dl/libltdl'
(cd mca/event/external && make  top_distdir=../../../../openmpi-master-201808100242-09ad725 distdir=../../../../openmpi-master-201808100242-09ad725/opal/mca/event/external \
    am__remove_distdir=: am__skip_length_check=: am__skip_mode_fix=: distdir)
make[3]: Entering directory '/mnt/data/nightly-tarball/scratch/openmpi/master-201808100242/ompi.git/opal/mca/event/external'
make[3]: Leaving directory '/mnt/data/nightly-tarball/scratch/openmpi/master-201808100242/ompi.git/opal/mca/event/external'
(cd mca/event/libevent2022 && make  top_distdir=../../../../openmpi-master-201808100242-09ad725 distdir=../../../../openmpi-master-201808100242-09ad725/opal/mca/event/libevent2022 \
    am__remove_distdir=: am__skip_length_check=: am__skip_mode_fix=: distdir)
make[3]: Entering directory '/mnt/data/nightly-tarball/scratch/openmpi/master-201808100242/ompi.git/opal/mca/event/libevent2022'
make[3]: *** No rule to make target 'distdir'.  Stop.
make[3]: Leaving directory '/mnt/data/nightly-tarball/scratch/openmpi/master-201808100242/ompi.git/opal/mca/event/libevent2022'
Makefile:2476: recipe for target 'distdir' failed
make[2]: *** [distdir] Error 1
make[2]: Leaving directory '/mnt/data/nightly-tarball/scratch/openmpi/master-201808100242/ompi.git/opal'
Makefile:2001: recipe for target 'distdir' failed
make[1]: *** [distdir] Error 1
make[1]: Leaving directory '/mnt/data/nightly-tarball/scratch/openmpi/master-201808100242/ompi.git'
Makefile:2102: recipe for target 'dist' failed
make: *** [dist] Error 2
FAILURE: <class 'subprocess.CalledProcessError'>: Command '['/home/mpiteam/ompi-scripts/nightly-tarball/run-with-autotools.sh', 'autotools/ompi-master', 'make', 'distcheck']' returned non-zero exit status 2

Build artifacts (including config.log and friends) are available at http://download.open-mpi.org/nightly/open-mpi/failed-builds/openmpi-master-201808100242-failed.tar.gz

It looks like the right libevent libraries are installed on the system, so with the recent change, the external libevent is being built and the libevent2022 component is not. The build error looks to be in the libevent2022 component.

+++ Configuring MCA framework event
checking for no configure components in framework event... 
checking for m4 configure components in framework event... external, libevent2022

--- MCA component event:external (m4 configuration macro, priority 90)
checking for MCA component event:external compile mode... static
checking --with-libevent-libdir value... simple ok (unspecified value)
checking for external libevent in... (default search paths)
checking event.h usability... yes
checking event.h presence... yes
checking for event.h... yes
looking for library without search path
checking for library containing event_config_new... -levent
checking if libevent requires libnl v1 or v3... 
checking for evthread_set_lock_callbacks in -levent... yes
checking for evthread_use_pthreads in -levent_pthreads... yes
checking if external libevent version is 2.0.21 or greater... yes
checking if MCA component event:external can compile... yes

--- MCA component event:libevent2022 (m4 configuration macro, priority 80)
checking for MCA component event:libevent2022 compile mode... static
checking if event external component succeeded... yes
configure: event:external succeeded, so this component will be skipped
checking if MCA component event:libevent2022 can compile... no
 
checking if have working event ops for the event framework... yes
checking for winning event component header file... external/external.h